Hey guys

Any experts out there... could you tell me what the problem might be? and how much would it involve/cost... thanks ps i havr posted this in the mods section becasue it falls into both.

I found an amp for sale with this description

Description of fault:

1. The amp runs perfectly for approx 30-60mins after turning on. Then it will lose 80% of its volume/power on Channel A only. Channel B is not affected and works perfectly when selected.

2. Blows the HT fuse intermittently – presumably this is related to the fault above.
I have had the amp looked at/serviced by a reputable repair technician with the following work carried out:
Replace 4 level control pots (Ch1 & Ch2)
Reduce gain on input stage
Install and bias new Output valves (4 x EL34 Electro-Harmonix)
Following this work, the amp runs quietly, with all controls working perfectly, however we have been unable to resolve the issue with Channel A losing volume after 30-60mins of use.

Ibanez SZ320
Randall RD75
Mesa boogie single recto series 2
Line 6 Toneport
Mesa boogie single recto series 1
Digitech GNX4
Last edited by gface at Jan 30, 2008,
Supp man!

You're probably facing heating issues with the amp, but is the most logical cause of the problem that I can think of. Just to be sure, open up the screws of the box and play with the speaker cone exposed, ensuring proper ventilation. If that sorts out your problem, you could install a small fan near the area which gets heated up the most.

Hope that helps!
Ya, probably heating, but also why post in 2 sections of the forum
Schecter C-1 Hellraiser
Ibanez EX 470 (1991)

Peavey 6505 combo
Vox Valvetronix AD15VT
Danville 1X12 Cab
Kustom 12w tube

Dunlop Crybaby
DOD overdrive(YJM)
Boss Ns-2
Dod 250 Overdrive